Divided Desert: New Wall & Biodiversity in the Borderlands.

The border between USA and Mexico spans approximately 2000 miles and the region has been under continuous socio-political and ecological struggles (Lorey, 1999). Mexico is the nearest and therefore the easiest way into the U.S. for the Latin-American organized crime cartels and the traffic between these nations creates social circumstances with the majority resulting in violence. The volume of illegal activity such as the movement of money, weapons, people and narcotics from all regions of Latin America have prompted federal departments from both nations to tackle these activities. The U.S proceeded more ambitiously compared to Mexico by building a non-continuous wall in 1994, composed of a series of approximately 15ft tall structures of rusted corrugated steel salvaged from the Vietnam war-era helicopter landing pads. During its construction a number of environmental laws were waived, and now scientist are beginning to identify the same problems that those laws were originally designed to prevent.

Dr. Rurik List from the Institute of Ecology at Universidad Nacional Autonoma de Mexico (UNAM) administers surveys of bison herds (Bison bison) that utilize aspects of habitat on both sides of the border in the Chihuahua desert (Figure 1). During their seasonal migration the buffalo have been spotted crossing the border which at the time was a broken-down barbwire fence that the buffalo broke themselves on earlier occasions (List et al. 2007). Meetings conducted with local ranchers on each side of the border highlight the importance of habitat use in these borderlands. Dialogues with the local rancher on the Mexican side indicated that several bison visited a pond on his land almost on a daily basis since it was the only year-round water source. In contrast, the American rancher explained how they came to a certain pasture on his land, where condition allow for a special kind of native grass (Schlyer. 2016).

range map
Figure 1. South limits of the historic range of American bison, highlighting paleontological, archaeological and historical accounts of species presence (List et al. 2017).

The current conditions on the border not only pose obstruction due to the barrier but the situation also brings road infrastructure, constant bright lights and border militarization which contribute to habitat degradation and anthropogenic pressures. The majority of the wall is not solid therefore small creatures such as reptiles, small mammals, insects and bugs can pass but the major concern lies on larger vertebrates. Such structures can divide populations and can pose a major threat on species genetics. For example, in the Arizonan side of the Sonoran Desert a herd of Pronghorn (Antilocapra americana) began to show low levels of reproduction after the construction of a segment of the wall. After further investigation, scientists learned that when the barrier was built, all the male pronghorn except for an old non-breeding male were separated by the fence (Heimbuch, 2014). When in non-breeding conditions male pronghorn disperse and live nomadic lives (Min, 1997). When the breeding season approaches the males return looking to reproduce but due to the construction of the barrier the herd was separated and unable to reproduce. Herds of wild herbivores in the south limits of their ranges have the potential to provide some of the necessary genetic material and along with it the associated physical adaptations that are required to survive and flourish in southwest North America. A man-made barrier dissecting these ranges and migration routes can pose additional complications to the already existing anthropogenic pressures that biodiversity face in the 21st century (Figure 2).

Figure 2. Some vertebrate taxa affected by the proposed wall in the Rio Grande riparian areas of southern Texas (University of Massachussets Amherst, 2016).

In south Texas the majority of the impacts have been habitat destruction and fragmentation much earlier than barrier problems. Government programs in the 1980’s paid ranchers to burn native thorn habitat then leading to construction of wall segments. The Rio Grande valley is of high biodiversity value because aside from semi-tropical and temperate zones meeting, it is also a geographic merger of  the two biogeographic realms of the Americas, the Nearctic and Neotropic. Due to these fusions, the fauna and flora that exist in this region does not appear anywhere else in the U.S. This is a major concern, such that if habitat degradation continues it will likely pressure certain species to local extinction levels which will cause ecological problems for the residents of borderlands. For instance, five of six North American cat species live in the border region and three of those species do not exist anywhere else north of that. The jaguar (Puma onca), ocelot (Leopardus pardalis) and jaguarundi (Herpailurus yagouaroundi) are classified as critically endangered in the U.S and despite other pressures their ability for these felids to migrate to and from Mexico will be crucial to their real recovery (Grigione et al. 2009) (Plate 1).

balance on the border
Plate 1. Adult mountain lion finding balance on the existing border wall (Arizona Fish & Game Department, 2017).

The major problem does not only lie in the damage inflicted to wildlife and landscapes but on the social and political realm of the situation. In 2005 the Real ID Act authorized the U.S Department of Homeland Security to waive all laws on the border to allow for intervention and construction of the barriers. Thirty seven laws have been dismissed in the region so far, including the Endangered Species Act, the Clean Air Act, the Clean Water Act, the Eagle Protection Act and many more (Nixon, 2017). The turndown of environmental law not only impacts species like puma, wolf, bear and deer but it sets a terrible example that it is acceptable for governments to ignore law and take action without considering the consequences to the natural world. With the recent proposals of the U.S government to build a more sophisticated wall (Figure 3) regardless of who pays for it, brings additional pressures on the wildlife local to the region.

trumps wall
Figure 3. Description of the proposed “Trump’s wall” in comparison to the existing structure (Al Jazeera, 2016).

The new wall is presented to be twice as high as the existing one and will be solid and mostly continuous (Plate 2). Eight designs from hundreds selected by the Customs and Border Protection (CBP) are in a bidding process. The concrete and steel edifices will be tested in various ways, particularly measuring the levels of difficulty to get across the barrier. Once selected new constructions plans will be in process across the 3,145 km border, costing an estimated $ 21 billion (Wong, 2017)

wall prototypes
Plate 2. Prototypes of the new border wall outside San Diego, California (Tuffs, 2017).

Donald Trump’s border narrative has met heavy opposition from the borderland communities such as lawmakers voting to expand funding to increase the use of technology and personnel instead of providing $ 3.6 billion for 100 miles of barrier (Wong, 2017). In addition, NGO’s have sued the Trump administration for failing to study the environmental impact and the decision to use law waivers is unconstitutional (Nixon, 2017). Organized crime on both sides and law enforcement can be thought of as two actors locked in constant competition, always attempting different methods to outsmart one another, with constant violent activity. The creations of their actions affect the landscape and its nature in drastic ways, this new barrier may just be another step in their evolution. For biodiversity, conservation plans and local residents this seems hopeless.

Solutions may lie in developing a more effective cross-boundary conservation mission and professionals need to collaborate more broadly on interdisciplinary issues. International cooperation such as assisted migration projects, mitigation for wildlife-crossing with a combination of mutual law enforcement, can lead to a much deeper understanding of this ecosystem flow. The Northern Jaguar Project based in Tucson, Arizona has been an example for such efforts (Plate 3) however homeland security issues will always focus on the human factors. By building cooperation and tolerance for each other on both sides, a collective binational solution can be produced. The conservation of the region’s natural heritage and maintenance of its complex processes are essential for the resilience and recovery of intrinsic value in the cognitive perspective of both nations.

sonoran jaguars
Plate 3. Pair of Sonoran jaguars stalk the borderlands in south New Mexico (Naturalia, 2015).



Grigione, M.M., K. Menke, C. Lopez–Gonzalez, R. List, A. Banda, J. Carrera, R. Carrera, A. J. Giordano, J. Morrison, M. Sternberg, R. Thomas, and B. Van Pelt. (2009) Identifying potential conservation areas in the U.S.–Mexico border region for neotropical cats: Integrating reliable knowledge at a landscape level. Oryx. 43:1 78-86.

Heimbuch J. (2014) How would a border wall between the U.S. and Mexico affect wildlife. Mother nature network Wilderness and Resources. December 4th

List, R., G. Ceballos, C. Curtin, P. J. P. Gogan, J. Pacheco y J. Truett. (2007). Historic distribution and challenges to bison recovery in the northern Chihuahuan Desert. Conservation Biology 21 1487–1494.

Lorey D. E. (1999) The U.S.-Mexican Border in the Twentieth Century. Wilmington: Scholarly Resources.

Min S. E. (1997) The effect of Variation in Male Sexually Diamorphic Traits on Female Behaviour in Pronghorn (Antilocapra americana). Ethology. 103. pp. 732-743.

Nixon, R. (2017) Homeland Security to Bypass Environmental Laws in Border Wall Works. New York Times: Politics, August 1st

Schlyer K. (2016) New Film: Border Walls and Boundaries.
(Acquired at: https://kristaschlyer.com/tag/border/)

Wong J. C. (2017) The shadow of Trump’s wall, locals remain unimpressed. The Guardian
Politics: Tuesday 24th October

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